The present invention relates to a system of mounting electronic parts onto a single-sided printing wiring board, and is particularly suitable for the manufacture of electronic equipment requiring key contacts, such as electronic calculators.
All conventional electronic equipment incorporating key contacts requires the key contact surface to be perfectly flat. To achieve this, manufacturers use a double-sided printed wiring board 1 as shown in FIG. 8, providing one of the surfaces 2 with a key contact pattern (not shown) and the other surface 3 with a variety of electronic parts 4. Both surfaces are electrically connected via through-holes 5. However, a double-sided printed wiring board 1 is relatively expensive. A single-sided printed wiring board as shown in FIG. 9 is more economical, but as the area peripheral to the key contact pattern 8 should be flat, such a board requires the key contact pattern area 8 to be separate from the electronic part mounting area 9. In consequence, a single-sided printed wiring board 7 is larger, going against today's trends towards miniaturization.